Characteristically, mines include a plurality of parallel entries extending from the mine opening to the face of the mine, wherein at least one of the entries serves as ventilation path through which air is furnished to the face of the mine. As the mine is dug deeper, crosscuts are provided at regularly spaced intervals. It will be appreciatd as the mine proceeds inwardly these crosscuts must be blocked to ensure that fresh air is continuously supplied to the mine face and so-called "stoppings" are used for this purpose. Although permanent or semi-permanent stoppings are generally used in practice, in many mines, such as metal mines, temporary changes are made in the ventilation on a day-to-day basis. It would be appreciated that permanent, and even semi-permanent, stoppings are obviously not suitable for this purpose because of the expense thereof and the installation time required.
Another use of mine stoppings, and one which is of importance here, is in mine disasters, such as mine fires, in shutting off or blocking a passage so as to re-establish or re-route ventilation as required. Again, stoppings used for this purpose must be established rapidly and many conventional stoppings simply cannot be used.
There are a number of patents which deal with stoppings used in mine ventilation control and reference is made to U.S. Pat. Nos. 1,478,303 (Snyder); 2,947,239 (Burgess); 3,118,363 (Burgess, Jr.) and 3,863,554 (Boyd) for a further discussion of the problems involved as well as the solutions that have been provided. Briefly considering these patents, the Snyder patent discloses a mine air stop in the form of a rigid frame having a textile covering thereon and including relief door hinged to the frame. The Burgess patent discloses ventilation control system in the form of a flexible sheet supported from the roof timbers and held down at the bottom by a weights (such as pieces of rock or coal). The Burgess, Jr. patent discloses a similar mine ventilation system wherein a mine ventilation sheet is supported by telescoping poles which extend between the floor and roof of the mine opening. The Boyd patent discloses a portable mine stopping wherein a sheet of fire resistant, gas impervious sheet is supported on a frame. Channel-like straps are adapted to compress edge portions of the sheet in sealing relationship with the walls of the mine opening (crosscut). In one embodiment of this patent the sheet is permitted to balloon out.